1. Field of the Invention
The present invention relates to wire bonding devices, and in particular, to such bonding devices that attach filament.
2. Related Art
Conventional systems and methods for attaching filament to devices, such as semiconductor chips or displays, typically include a spool of filament, a de-spooler to unwind the filament, a dancer arm with a pulley to adjust tension in the filament as it is unwound, a filament guide, and an attaching means for attaching the filament. The attaching means may be a welding device, such as a laser welder or ultrasonic bonder. The device onto which the filament is to be attached can be held in place, while the attaching means moves to attach the filament at the selected portions of the device. Other types of spooled lines, such as bond wires, may utilize similar structures and methods.
Conventional devices include support structures onto which the filament is stretched across and attached, such as described in U.S. Pat. No. 6,509,693 to Yonezawa et al, which is incorporated by reference in its entirety. The support structures provide, in part, separation from underlying elements. This separation prevents the filament from sagging and contacting the underlying elements after the filament has been heated and expands. The structures allow each of the filaments to be fixed at one end and elastically held at the other end.
However, such a system can be costly due to the additional expense of manufacturing and securing the support structures onto the device. Furthermore, the support structures increase the overall thickness of the device. Moreover, the welding of the filament to the support structures may cause the filament coating, e.g., carbonate, to scatter into display areas of the device, thereby resulting in inferior or damaged displays.
U.S. Pat. No. 6,509,693, incorporated above, discloses another filament attachment system in which the filament is bonded between a wiring layer and a metal foil or wire. This requires two bonds or materials to secure the filament.
Accordingly, there is a need for a system for attaching filaments that overcomes the deficiencies in the prior art as discussed above.